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Chemistry II

oL4

24lttl 2oL7 O8.3O AM - 11.30 AM

Ruranda Edu*a .rfi 8$a

ADVANCED LEVEL NATIONAL EXAMINATIONS, 2OL7

SUBJECT: CHEMISTRY

PAPER

II: THEORY

CoMBINATIONS: - BIOLOGY-CHEMISTRY-GEOGRAPHY (BCGI

- MATHEMATICS-CHEMISTRY-BIOLOGY (MCBI

- PHYSICS-CHEMTSTRY-BIOLOGY (PCB)

- PHYSICS-CHEMISTRY-MATHEMATICS (PCM)

DURATION: 3 HOURS

INSTRUCTIONS:

1. Write your names and index number on the answer booklet as written on

your registration form, and DO NOT write your names and index number

on additional answer sheets of paper if provided.

2. Do not open this question paper until you are told to do so.

3. This paper consists of two sections: A and B.

section A: Attempt all questions.

4.

section B: Attempt any three questions.

A sample of the Periodic Table is provided on page 8'

5. Silent non-programmable calculator may be used'

6. Use a blue or black Pen.

O14-Pagelof8

(TOmarks)

(3omarks)

SECTION A: Attempt aU questions. (Tomarksf

1) (a) Describe the term "covalent

bond".

(2marks)

(b) Draw diagrams to show the shapes of the following molecules

and in each case state the narne of the shape.

(i) BeClz

(ii) BFs

(Smarksf

(iii) SFo.

(Atomic number: Be=4, Cl=L7, B:5, F:9, S:16)

2) Explain the following observations:

,*(a)

In group [a of the periodic table, metallic character increases as

you

move down the

group.

(2marks)

(b) The shape of COz (carbon dioxide) is linear whereas

water (HzO) is bent

(V-shaped).

that of

(4marksf

(Atomic number: C:6, O=8, H=1)

3)

(a) Complete this radioactive series:

a po d >pb 0- >Bi q >Tt F- >pa

'33*" --q-->Rn >

(Bmarks)

(b) A stable nuclide absorbs a neutron, emits an electron, and then

splits into two o particles. Identifii the nuclide.

(3marks)

(c) (i) One can produce sodium-24 by exposing stable sodium

?1*"

to a flux of neutrons. Write down the formation reaction of

sodium-24.

(lmark)

(ii) Sodium-24 is radioactive by emission of B- and its half-life is

15 hours. Write down the equation for the decay of sodium-24.

(lmarkf

(iii) One injects into the blood of an individual 10cm3 of a solution

initially containing sodium-24 witl: a concentration of 10-smo1.l-1.

What is the number of moles of sodium-24 that have been injected

into the blood? How much of it will remain after 6 hours?

(2marks!

4l Zinc oxide, ZnO is amphoteric. It dissolves in alkali

to give the

ion Zn(OHl+z-.

Write the ionic equation for the reaction between ZnO and

sodium hydroxide in water.

(b) Write the equation of reaction of ZnO with hydrogen ions.

(a)

^rr

Ji U't:

{:

-11 4

:7

014-Page2of8

(2marks|

(2marks|

Mn(OH)z is made by adding an alkali to a solution containing

illtnz* ions, the wirite precipitate formed quickly turns to brown and

eventually goes black in an open test tube'

Write the chemical formula of the compound that forms:

(lmark)

(i) Brown preciPitate.

5)' (a) When

(lnarkf

(ii) Black preciPitate.

(b) Write a chemical reagent that you would use to distingUish between

a11d.Zn2* ions in solution indicating the observable change and

'-'**r*

a chemical equation for a positive test if possible in any

case'

(Smarks|

(NO) can be converted to nitrogen dioxide (NOz) gas

acid is to be manufactured:

6) Nitrogen monoxide

when nitric

2

NO1g)

+

2 NOztgl AH: -114 KJ mol-l

OzG)

(a) State the colour of NOz gas.

(b) State and explain the effect of reducing pressure of the reacting

'

' mixture to the position of equilibrium.

(lmark)

(2marks)

-

7l Acetone and ethyl acetate are organic liquids that form an ideal

mixture and are used as solvents. At 300C, the vapour pressure

of pure acetone is 285 mmHg and the vapour pressure of pure

ethyl acetate is 118 mmHg.

Caltuhte the total vapour pressure at 30oC of a solution prepared

(Smark'sf

by dissolving 25.09 of acetone and 225 gof ethyl acetate.

(Molar *a"", Acetone = 58.0 g mol-t , ethyl acetate = 88 g mol-l )

various factors that affect the speed of migration of ions

in solution during electrolYsis.

(Smarks|

Mention 3 of those factors.

8) (a) There are

(b) Explain the reason why lithium ion, Li* moves through a solution

' ' less rapidly than other cations such as Na* during electrolysis,

despite the fact that

e)

it (Li.) is far smaller than other metal ions. (2marks|

An organic compound of 5.0 g by mass is dissolved in 100 g of

oC. The boiling

benzene. The boiling point of this solution is 82-42

point of pure benzene is 80.10 oC;

(4marksf

Calculate the molar mass of the organic compound'

(Ebullioscopic constant, Kb= 2.53 oC/m and m=moI Kg-t1

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1O)

Write chemical equations of reaction (structural formulae) of

the organic compounds given below and the products formed.

(a) 2-Pentene + ozorLe ----------------)

(2marks)

(b) 2-Methyl 3-hexene + MnO+- --Wder-->

(2marksf

11) By giving appropriate reagents to be used in different equations

of the steps of synthesis, write equations of reaction that enable

the synthesis of methyl amine (CHsNHz) from chloroethane

(3marks)

(CHsCHzCI).

I2l

structural formulae and write the IUPAC names

(scientific names) of the products resulting from the reaction

of lithium aluminium hydride and the following compounds:

(i) Ethanal.

(a) Draw the

(b).

(ii) 2-pentanone.

(2marks)

(2marksf

Write the structural formulae of compounds obtained by the

reaction of 3-butanone and iodine in the presence of sodium

hydroxide.

(2marks)

13) (a) Octane can be cracked and converted into pentane and

substance B (hydrocarbon).

Give the name of substance

B.

(lmarkf

(b) To improve octane's ability to behave as a good fuel,

it undergoes

catalytic reforming to obtain a branched isomer C.

Draw the structure of isomer C and give its IUPAC name.

14) The dissociation constant of ammonia

is 1.8

x 10-s.

Calculate the pH of aO.2 mole/litre solution of ammonia.

NHs +

HzO ryethane) is an organic compound, (CHsCHzO)z;

(a) Write an equation of reaction

including structural formula of

Reactants to produce ethoxyethane.

(b) Mention 2'uses of ethoxyethane.

Ol4-Page4of8

(2marks)

(2marks)

SECTION B: Attempt only three questions.

(3Omarksl

16) (a) Ammonia is manufactured by Haber-Bosch process. Explain

how nitrogen to be used in this process is obtained on a large

scale.

(2marksl

(b) The manufacture of ammonia requires Ne and Hz gases.

Production of hydrogen gas (Hz) requires a two stage process,

primary and secondary reforming in which a mixture of

hydrocarbons (naphtha) is passed in steam over a nickel catalyst.

Primary staee

CH+(gl +

HzOB

COrd + 3

Secondary stage

HzB

AH: positive

:

cot*l + Hzo(s)

+ HzE)

611= positive

-

(i)

(ii)

Briefly state a chemical substance that can be used to remove

COz gas from the by-products of the reaction.

Explain the necessity of the use of nickel

(lmarkt

catalyst.

(lmarkf

-CozB

(iii) If 60 dms of CH+

- of gas were made to react completely with

6O dms of HzO gas; calculate the volume of Hz gas produced in

the primary

stage.

(2marks)

(iv)State and explain the effect of reducing pressure to the position

of equilibrium in the primary stage reaction.

(2marks)

(c)

i

t

Ammonia is used to produce nitric acid; this requires the reaction

between NHe and Oz to produce NO gas.

Write a balanced chemical equation of reaction between NHs and

Oz to get NO gas.

(2marks)

17) (a) Given the following molar conductivities at infinite dilution A-

:

NaCl= 126.4, NaOH:248.4, NH+CI=149.8, Na*=50. 1, OH-= 198.3,

CI-=7 6.3.

(Units of molar conductivity at infinite dilution (A-) are: S cm2

Calculate the molar conductivity of NH+OH at infinite

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mo1-1).

dilution.

(Smarks)

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